This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-039461, filed Feb. 18, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to an information storage medium which records video data sent in, e.g., digital broadcast, or stream data sent with a packet structure. Further, the present invention relates to a data structure of management information that pertains to stream data recorded on the medium. Still further, the present invention relates to a recording method and playback method of the management information.
In recent years, TV broadcast has come into the era of digital broadcast. Accordingly, an apparatus for saving digital data of digital TV broadcast as it is irrespective of their contents, i.e., a so-called streamer, has been demanded.
The current digital TV broadcast uses an MPEG transport stream. In the future, an MPEG transport stream will be used as a standard one in the field of digital broadcast using moving picture.
In such digital broadcast, the contents (mainly, video information) to be broadcasted are time-divided into groups of data each having a predetermined size (e.g., 188 bytes) called transport packets, and broadcast data is sent in units of transport packets.
As a streamer for recording digital broadcast data, a home digital VCR such as D-VHS (digital VHS) or the like is currently commercially available. A streamer using D-VHS directly records a broadcasted bitstream on a tape. For this reason, a plurality of programs are multiplexed and recorded on a video tape.
Upon playback, all data are output from the VCR to a set-top box (digital TV reception apparatus; to be abbreviated as an STB hereinafter) either when they are played back from the beginning or the middle of the tape. In this STB, a desired program is selected from the output data by user operation or the like. The selected program information is transferred from the STB to a digital TV receiver, and is played back (playback of video plus audio, etc.).
Since this D-VHS streamer uses a tape as a recording medium, it cannot attain quick random access, and it is difficult to quickly jump to a desired position of a required program so as to play it back.
As a promising candidate that can combat such shortcoming (difficulty of random access) of the tape, a streamer that uses a large-size disc medium such as a DVD-RAM or the like has been proposed. In this case, management data must be inevitably recorded together with broadcast data in consideration of random access, special playback, and the like.
Note that a digital interface that complies with IEEE1394 or the like can be used in data transfer between the STB as a digital TV receiver and the stream that uses large-capacity disc media such as a DVD-RAM and the like, or between the streamer that uses large-capacity disc media and another streamer using a D-VHS or the like.
In this digital interface, video data/stream data are transferred in units of transport packets received in digital broadcast.
For example, in a digital interface using IEEE1394, time stamp data indicating the reception time is appended to each transport packet to guarantee real-time transfer of digital broadcast reception data, thus transferring the data.
Also, in order to guarantee real-time, seamless playback of the digital broadcast reception data recorded on an information storage medium such as a DVD-RAM or the like, the time stamp data is simultaneously recorded together with each transport packet data.
In the aforementioned case, as stream data to be recorded on an information storage medium that uses large-capacity disc media such as a DVD-RAM and the like, each transport packet is recorded while being appended with time stamp data. For this reason, time management is made using this time stamp data.
In digital TV, video data is broadcasted while its information is compressed using a digital compression scheme called MPEG2. In MPEG2, P-picture information has only differential information from I-picture, and B-picture information has only differential information from I- and P-pictures. Therefore, B- or P-picture cannot be solely played back, and playback from I-picture is required to playback these pictures.
Note that the video playback time viewed from the user, which is indicated by display times of I-, B-, and P-pictures, is different from the time stamp information. For this reason, when time management for stream data recorded on the information storage medium is made using only the time stamp data, control of the display time (video playback time) for the user cannot be accurately made.
The present invention has been made to solve the aforementioned problem, and has as its object to provide a data structure of management information, and a recording method and playback method of the same, which make time management of stream data using time stamp data recorded in the stream data, and can make accurate time display control for the user.
In order to achieve the above object, according to the present invention, information (time relationship table; or playback time stamp list PTSL) that indicates the relationship between time stamp data (application time stamp ATS) recorded in stream data, and display time information (PTS or field information) for the user is provided to a portion of management information (stream file information table SFIT).
On the other hand, the relationship among the display time information (PTS or field information) for the user, the start time position of each I-picture (or access unit start map AUSM indicating stream object unit SOBU to which target access unit AU belongs), and time stamp data (ATS) can be indicated by the time relationship table (or PTSL).
An information medium according to the present invention has a data area (STREAM.VRO/SR_TRANS.SRO) where stream data (SOB or SOBU) can be recorded in a predetermined data recording unit (transport packet/application packet), and a management area (STREAM.IFO/SR_MANGR.IFO) where management information (STRI) that pertains to the stream data can be recorded. The management information (STRI) can record: first management information (ATS corresponding to I-picture transfer start time; or AUSM) used to access the stream data (access I-picture information or AU); and third management information (time relationship table; or PTSL) which is different from the first management information (AUSM), and indicates a relationship between the first management information and second management information (PTS; or cell start APAT=SC_S_APAT) used to access the stream data.
A recording method according to the present invention uses an information medium (201) which has a data area (STREAM.VRO) where stream data (SOB or SOBU) can be recorded in a predetermined data recording unit (packet), and a management area (STREAM.IFO) where management information (STRI) that pertains to the stream data can be recorded. The management information (STRI) can record: first management information (ATS corresponding to I-picture transfer start time; or AUSM) used to access the stream data (access I-picture information or AU); and third management information (time relationship table; or PTSL) which is different from the first management information (AUSM), and indicates a relationship between the first management information and second management information (PTS; or SC_S_APAT) used to access the stream data (AU).
Upon recording on such information medium, the first management information (ATS/AUSM) is extracted from stream data to be recorded (step S03); the second management information (PTS) is extracted from the stream data to be recorded (step S04); the stream data (packet data) is recorded on the information medium (201) (step S07); and the third management information (time relationship table/PTSL) is recorded on the management area (STREAM.IFO/SR_MANGR.IFO) (step S11).
Alternatively, upon recording on such information medium, a synchronization process of a predetermined reference clock (SCR) is executed between a stream data supply device (STB unit) and a stream data recording device (optical disc device or optical disc drive) (step S54); the third management information (time relationship table; or PTSL) is corrected or modified on the basis of a result of the synchronization process of the reference clock (SCR) (step S56); and the corrected or modified third management information (time relationship table; or PTSL) is recorded in the management area (STREAM.IFO/SR_MANGR.IFO) on the information medium (201) (step S57).
A playback method according to the present invention uses an information medium (201) which has a data area (STREAM.VRO/SR_TRANS.SRO) where stream data can be recorded in a second data unit (SOBU) including a first data recording unit (application packet AP), and a management area (STREAM.IFO/SR_MANGR.IFO) where management information (STRI) that pertains to the stream data can be recorded. The management information (STRI) can record: first management information (ATS corresponding to I-picture transfer start time; or AUSM) used to access the stream data (access I-picture information or AU); and third management information (time relationship table; or PTSL) which is different from the first management information (AUSM), and indicates a relationship between the first management information and second management information (PTS; or SC_S_APAT) used to access the stream data (AU).
Upon playing back the stream data from such information medium (201), when the stream data has a plurality of continuous second data units (for example, SOBU#1 and SOBU#2), a position difference (PTS offset or AP which is not played back in FIG. 29(g)) from a neighboring boundary position of the plurality of continuous second data units (SOBU#1 and SOBU#2) to a position (SC_S_APAT) of the first data recording unit (AP) indicated by the second management information (PTS; or SC_S_APAT) is checked (step S24); read of the stream data recorded on the information medium (201) starts from the neighboring boundary position (step S30) but read data until the position (SC_S_APAT) of the first data recording unit (AP) indicated by the position difference are discarded or ignored (step S31); and playback (display of playback information) of the stream data recorded on the information medium (201) starts from the position (SC_S_APAT) of the first data recording unit (AP) indicated by the position difference (step S32).
Alternatively, upon playback from such information medium, a start address of the second data unit (SOBU) including the first management information (ATS corresponding to I-picture transfer start time; or AUSM) is checked (step S45); playback information other than an access position (access position of I-picture information or AU) of the stream data indicated as the first management information (AUSM) is discarded or ignored using the checked start address of the second data unit (step S47); and only playback information at the access position (I-picture information; or AU) of the stream data is sequentially played back or displayed (step S49).
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.